The next step was to machine the areas where the bolt carrier rides straight and make some filler sections with the internal profile and fit them up.
First I welded in the lower filler blocks, removed the section from the jig and fitted the carrier. Then I welded in the upper fillers and checked the carrier fit. When both sides were done I cut some .070" fillers for the thin sections and welded them in.
The first photo shows the center area welded and rough ground. There is still a small area under the feed tray that needs to be filled. You can see in the rear the lower and upper fillers have been tacked in and the center section is ready to be cut with smooth parallel edges for a filler section.
The next photo shows the upper rear filler welded in and partially machined. The sides need to be machined and the area in front of the ears needs to be cut to radius.
The next photo shows the rear fillers welded in before machining and grinding. There are a few more spots that need fillers and welding. The carrier rides smoothly, the bolt locks up and the rear cap also fits properly.
Here is the receiver with the welding completed and most of the areas rough ground.